System and method for capturing images of a target area on which information is recorded

ABSTRACT

A system for capturing images of a target area on which information is recorded includes a boom assembly adapted to extend outwardly from a generally vertical surface. At least one digital camera is mounted on the boom assembly at a location spaced from the surface. The at least one digital camera is oriented so that the field of view thereof encompasses a target area on the surface. A controller is in communication with the at least one digital camera. The controller conditions the at least one digital camera to acquire an image of the target area. The image acquired by the at least one digital camera is conveyed to the controller and is processed to determine if an obstacle blocking the target area is in the captured image. If so, the captured image is not further processed and additional images are acquired until an image of the target area is captured without the obstacle therein.

FIELD OF THE INVENTION

The present invention relates generally to image acquisition and inparticular to a system and method for capturing images of a target areaon which information is recorded.

BACKGROUND OF THE INVENTION

During meetings, boards such as whiteboards, chalkboards, flipchartpads, and tackboards are commonly used to record information. Incollaborative environments, several users may view, supplement and/oredit information recorded on the boards. In situations where the boardsare passive, it is difficult and cumbersome to transfer informationrecorded on the boards to other media that facilitate storage andretrieval of the recorded information.

To deal with the above problem, automated capture systems to captureinformation recorded on a board have been considered. These automatedcapture systems include for example, automated copyboards, flipchartscanners, active or specialized pen systems based on acoustictime-of-flight, electromagnetic detection, or laser scanning as well asanalog resistive whiteboards.( Although these automated capture systemshave permitted information recorded on a board to be transferred toother media types, these automated capture systems suffer disadvantages.

In addition to the automated capture systems described above,camera-based systems to capture information recorded on a board havebeen considered. For example, U.S. Pat. No. 5,528,290 to Saund disclosesa device for transcribing markings drawn on a whiteboard or blackboardinto an electronic form using a camera-based board scanner. The scanneris in the form of a video camera mounted on a computer controlledpan/tilt head suspended from the ceiling or mounted to one side of theboard. The camera is directed successively at small regions (tiles) ofthe board and snapshots of the tiles are captured until a complete imageof the entire board is obtained. The camera image tiles slightly overlapwith neighboring camera image tiles so that a complete image of theboard is obtained with no missing spaces.

U.S. Pat. No. 5,581,637 to Cass et al discloses a device fortranscribing markings drawn on a background surface such as a whiteboardor blackboard into an electronic form using a video camera. Aregistration light pattern is projected onto the background surface tobe imaged. The projected pattern is selected to suit the properties ofthe video camera and the imaging environment. The video camera isdirected successively at tiles of the background surface and snapshotsof the tiles are captured until a complete image of the entirebackground surface is obtained. The pattern markings are processed usingperspective transformations to determine the overlap properties of thecamera image tiles and the distortion of each camera image tile. Theresulting data is used to combine the camera image tiles to produce anundistorted image of the entire background surface.

U.S. Patent Application Publication No. US2004/0201698 to Keenan et al.discloses a camera-based system for capturing images of a backgroundsurface such as a whiteboard. The camera-based system includes agenerally horizontal boom assembly mounted above the whiteboard thatsupports a plurality of cameras. The cameras look back at the whiteboardand are actuable to capture images of sections of the whiteboard. Thecamera images are stitched to form an entire image of the whiteboard.

In the above-described camera-based systems, it is typically desiredthat all information recorded on the background surface be captured inimages acquired by the cameras. Unfortunately, in some instances imagesof the background surface are captured and processed when an obstaclesuch as a person, a piece of furniture or other object obscures aportion of the background surface from the fields of view of thecameras. The end result is incomplete images and wasted processing andmemory resources. As will be appreciated, improvements in systems ofthis nature to obviate or mitigate the above disadvantage are desired.

It is therefore an object of the present invention to provide a novelsystem and method for capturing images of a target area on whichinformation is recorded.

SUMMARY OF THE INVENTION

According to one aspect of the present invention there is provided asystem for capturing an image of a target area on which information isrecorded comprising:

at least one imaging device capturing an image of said target area; and

a processor in communication with said at least one imaging device, saidprocessor receiving image data from said at least one imaging device andprocessing said image data to detect the presence of obstacles in thecaptured image.

According to another aspect of the present invention there is provided acamera-based system for capturing an image of a target area comprising:

a generally horizontally extending boom assembly, said boom assemblybeing positioned above a target area on which information is recorded;

at least one digital camera mounted on said boom assembly at a locationspaced from the plane of said target area, said at least one digitalcamera being oriented so that the field of view thereof encompasses saidtarget area; and

a processor in communication with said at least one digital camera, saidprocessor receiving image data from said at least one digital camera andprocessing said image data to detect the presence of an obstacle in thecaptured image, said processor conditioning said at least one digitalcamera to acquire another image of said target area in the presence ofan obstacle in said captured image.

According to yet another aspect of the present invention there isprovided a method of detecting the presence of an obstacle in front of abackground surface on which information is to be recorded, in a capturedimage of said background surface, said method comprising the steps of:

comparing the captured image with a reference image and computing adifference image; and

examines the difference image to determine of the difference image haspixels suggestive of an obstacle.

According to still yet another aspect of the present invention there isprovided a method of capturing and storing images of a backgroundsurface on which information is recorded, said method comprising thesteps of:

capturing a low resolution image of the background surface;

processing the low resolution image to determine if an obstacleobscuring the background surface is in said low resolution image; and

if no obstacle is in said low resolution image, capturing a highresolution image of said background surface.

According to still yet another aspect of the present invention there isprovided a method of capturing and storing images of a backgroundsurface on which information is recorded, said method comprising thesteps of:

capturing an image of the background surface;

processing the image to determine if an obstacle obscuring thebackground surface is in the captured image; and

processing the captured image to highlight information recorded on thebackground surface when no obstacle is in said captured image.

The present invention provides advantages in that since captured imagesare analyzed to detect the presence of an obstacle therein, when anobstacle is detected in a captured image, the captured image is notprocessed further thereby saving computing resources and memory. Also,by taking successive images and determining when an obstacle moves outof the field of view, the change in obstacle detection can be used as acue to process the captured image devoid of the obstacle.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described more fullywith reference to the accompanying drawings in which:

FIG. 1 is an isometric view of a camera-based system for capturingimages of a target area on which information is recorded in accordancewith the present invention;

FIG. 2 is an exploded isometric view of a boom assembly forming part ofthe camera-based system of FIG. 1;

FIG. 3 is a block diagram of a digital camera forming part of the boomassembly of FIG. 2;

FIG. 4 a is a front elevational view of a controller forming part of thecamera-based system of FIG. 1;

FIG. 4 b is an isometric view of the controller of FIG. 4 a;

FIG. 5 is a block diagram of the controller internal circuitry;

FIG. 6 is a flowchart illustrating the steps performed by thecamera-based system of FIG. 1 during image capture and processing;

FIG. 7 is a flow chart illustrating the steps performed by thecamera-based system during obstacle detection; and

FIG. 8 is an isometric view of a camera-based system for capturingimages of a target area including a whiteboard with an optical switch.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention relates generally to a system and method forcapturing an image of a target area on which information is recorded. Atleast one imaging device is actuable to capture an image of the targetarea. A processor communicates with the at least one imaging device andprocesses image data received from the at least one imaging device todetect the presence of an obstacle in the captured image. In this mannera decision can be made as to whether the captured image is to be furtherprocessed. Preferred embodiments of the present invention will now bedescribed with reference to FIGS. 1 to 8.

Turning now to FIG. 1, a camera-based system for capturing images of abackground surface and automatically posting the images to an Internetaccessible site in accordance with the present invention is shown and isgenerally identified by reference numeral 20. System 20 is similar tothat disclosed in U.S. Patent Application Publication No. US2004/0201698to Keenan et al. filed on Jun. 8, 2001, assigned to SMART TechnologiesInc., assignee of the present invention, the content of which isincorporated herein by reference. As can be seen, the system 20 includesa whiteboard 22, defining the background surface to be imaged, that ismounted on a wall surface. In this embodiment, the whiteboard 22includes a generally planar rectangular board surface 22 a bordered by aframe 22 b. An elongate tool tray 24 is disposed slightly below thewhiteboard 22 and supports tools in the form of dry-erase ink pens andan eraser. Using the pens and eraser, information can be recorded on thewhiteboard 22, as well as edited and erased. In FIG. 1, a circle, asquare and a triangle have been drawn on the surface 22 a of thewhiteboard 22.

A boom assembly 26 is also mounted on the wall surface slightly abovethe midpoint of the whiteboard 22. The boom assembly 26 extendsoutwardly from the wall surface in a generally horizontal disposition adistance equal to about 30 to 50 inches. A controller 30 is also mountedon the wall surface to one side of the whiteboard 22 and communicateswith the boom assembly 26 and with a distributed computer network 40.

FIG. 2 better illustrates the boom assembly 26 and as can be seen, boomassembly 26 includes a wall mount 50 receiving one end of an elongatedboom 52. Wall mount 50 has a plurality of slots 54 formed in its rearsurface. The slots 54 releasably receive complimentary tabs 56 on amounting plate 58 that is secured to the wall surface by suitablefasteners (not shown). The wall mount 50 also includes a pivoting cap 60that can be moved to expose a pair of plug-in high speed serial datacommunication ports (not shown). One of the data communication portsreceives a cable 62 that extends to the controller 30. The other datacommunication port is designed to receive a cable leading to the wallmount of an adjacent boom assembly when a number of whiteboards and boomassemblies are arranged in a side-by-side chain.

A camera head 68 is disposed on the opposite end of the boom 52 andsupports a pair of imaging devices in the form of digital cameras 70 aand 70 b. The digital cameras 70 a and 70 c are aimed back towards thewhiteboard 22. Each digital camera is fitted with an appropriatefield-of-view lens so that it captures a different section (tile) of thewhiteboard 22. The field-of-view lenses are however selected so thatthere is a small overlap in the images captured by the digital cameras70 a and 70 c.

Turning now to FIG. 3 the digital cameras 70 a and 70 c within thecamera head 68 are shown. As can be seen, each digital camera includes alens system 72 and an image sensor 74. A digital signal processor (DSP)engine 76 is connected to the image sensor 74 and to the high-speedserial data communication ports by cables (not shown) running throughthe boom 52.

FIGS. 4 a to 4 b better illustrate the controller 30. As can be seen,controller 30 includes a housing 80 having a liquid crystal displayscreen 82 and a series of user selectable controls in the form ofdepressable buttons. In this particular embodiment, the buttons includea session open button 84, a session close button 86 and a capture imagebutton 88. A pair of scroll buttons 90 a and 90 b allow a user to scrollthrough features presented on the display screen 82. Buttons 92 a to 92d allow features presented on the display screen 82 to be selected.

FIG. 5 illustrates the internal circuitry 98 within the housing 80. Ascan be seen, the internal circuitry 98 includes a central processingunit (CPU) 100 communicating with a high speed serial data communicationport 102, a printer interface 104, an LCD video display and a keypaddriver 106, a network interface controller 108 and memory 110.High-speed data communication port 102 receives the cable 62 leading tothe boom assembly 26. LCD video display and keypad driver 106 drives thedisplay screen 82 and the buttons 84 to 92 d. Printer driver 104 iscoupled to a port accessible through the housing 80 that is designed toreceive a cable extending to an external printer. Printer driver 104 isalso coupled to the network interface controller 108.

The central processing unit 100 includes Internet server capabilitiesand executes software loaded in the memory 110 so that image data outputby the digital cameras 70 a and 70 c can be processed, converted intodigital images in JPEG format and made accessible to users through thedistributed computer network 40. In this manner, users can access thedigital images through web client applications such as web browsers.Further specifics concerning the operation of the system 20 will now bedescribed with particular reference to FIGS. 6 and 7.

Using the system 20 is very simple regardless of the technical skilllevel of the user. The controller 30 does not need to be operationalprior to drawing or writing on the surface 22 a of the whiteboard 22.Once information is recorded on the surface 22 a of the whiteboard 22,images of the recorded information can be acquired provided a session isopen. If a session is not open, the user must press the session openbutton 84 to open a session. When the session open button is pressed,the CPU 100 creates a session so that all images captured within theopen session are stored collectively.

Once a session has been opened, when the capture image button 88 ispressed the digital cameras 70 a and 70 c are conditioned by the DSPengine 100 to capture low resolution images of the whiteboard 22 andsurrounding area (see step 120 in FIG. 6). In the present embodiment,the resolution of these images is 302×217. After each digital camera 70and 70 c has captured a low resolution image of the whiteboard 22, theraw image data from the image sensors 74 is acquired by the DSP engine76 and conveyed to the CPU 100 over a high speed data communicationslink via the cable 62. When the CPU 100 receives the image data, theimages are cropped and mapped into a rectangle to limit the images tothe whiteboard area (step 122). In order to enable the images to becropped and mapped, during initialization of the system, 20, targets areplaced at the corners of the surface 22 a and images are captured. Thelocations of the targets are then detected in the captured images andare used to extract points that delineate the whiteboard area and allowthe whiteboard area to be mapped into the rectangle. The extractedpoints are stored in memory and are used each time whiteboard images arecaptured so that the captured images can be cropped and mapped into therectangle (i.e. limited to the appropriate area of interest).

Once the images have been cropped and mapped into the rectangle, theimages are cleaned to remove noise and unwanted speckles from the image(step 124). During image cleaning, background shades of white created invarious lighting conditions are removed so that only high contrast penstrokes on a white or empty background remain. The image cleaningprocess is disclosed in U.S. Patent Application Publication No.US2003/0156118 to Ayinde, assigned to SMART Technologies Inc., assigneeof the present invention, the content of which is incorporated herein byreference. Accordingly, specifics of the image cleaning process will notbe described herein.

Once the images have been cleaned at step 124, the images are stitchedby the CPU 100 (step 126). In order to stitch adjacent images together,the surface 22 a of the whiteboard includes target references orcross-hairs (not shown) thereon that are positioned so each imageincludes a common pair of target references. The common targetreferences allow the images to be easily stitched together by the CPU100. Other image stitching methods can of course be used such as thatdisclosed in U.S. Pat. No. 5,528,290 to Saund.

After stitching at step 126, a check is made to determine if a referenceimage exists (step 128). If not, the image is stored as a referenceimage (step 130) and the process returns to step 120. If a referenceimage exists, the whiteboard image is analyzed to determine if anobstacle is present in the image (step 132). In order to determine if anobstacle is present in the whiteboard image, binary versions of thereference and whiteboard images are computed (see step 140 in FIG. 7). Adifference image is then calculated using the binary versions of thewhiteboard image and the reference image (step 142). During generationof the difference image, the negative of the difference between the twoimages is computed by comparing the whiteboard and reference imagespixel by pixel. For every corresponding pixel in both images thefollowing value is computed:(255−|R _(ij) −C _(ij)|)where:

R_(ij) is the binary form of the pixel at the i^(th) row and j^(th)column in the reference image (255 for white, 0 for black); and

C_(ij) is the binary form of the pixel at the i^(th) row and j^(th)column in the whiteboard image.

This yields a black on white image where pixels having different valuesin the two images are set to black and pixels having the same values inthe two images are set to white. The difference image is then cleanedagain using median filtering performed in N iterations to remove noiseand unwanted speckles from the computed negative difference image (step144). It has been found that N=3 yields good results in a variety ofconditions although N can be varied.

The number of pixels in the cleaned difference image that are black isthen determined (step 146) and compared to a threshold value (step 148).If the number of pixels in the difference image having a black value isgreater than the threshold value, an obstacle is deemed to be present inthe whiteboard image. Typically a change in the number of black pixelsbetween a whiteboard image and the reference image greater than about 2%signifies the presence of an obstacle.

If an obstacle is determined to be in the whiteboard image at step 132,the whiteboard image is not processed any further. The process thenreverts to step 120 where the CPU 100 conditions the digital cameras 70a and 70 c to capture low resolution images again. This processcontinues until the digital cameras 70 a and 70 c capture low resolutionimages devoid of an obstacle. During this routine, if an obstacle ispresent in the captured low resolution images for a threshold number ofconsecutive frames or a threshold period of time, the CPU 100 stores thewhiteboard image as the new reference image (step 130) and conditionsthe digital cameras 70 a and 70 c to acquire high-resolution images ofthe whiteboard 22 (step 134). As will be appreciated, since capturedimages having obstacles detected therein are generally not stored orprocessed any further after the obstacles have been detected, memory andprocessing resources are conserved.

At step 132, when no obstacle is present in the whiteboard image, theCPU 100 stores the whiteboard image as the new reference image (step130) and conditions the digital cameras 70 a and 70 c to acquirehigh-resolution images of the whiteboard 22 (step 134). In the presentembodiment, the resolution of these images is 2100×1564. After thedigital cameras 70 a and 70 c have acquired high-resolution images ofthe whiteboard 22, raw image data from the image sensors 74 is acquiredby the DSP engines 76 and conveyed to the CPU over a high speed datacommunications link via the cable 62. When the CPU 100 received the rawimage data, the CPU converts the raw image data into color images andcrops and maps the high-resolution image into a rectangle to limit theimage to the whiteboard area. The CPU 100 then stitches the imagestogether to form a complete image of the whiteboard 22 and thehigh-resolution image is cleaned in the manner discussed above. With thehigh-resolution image cleaned, the CPU 100 conditions the LCD videodisplay and keyboard driver 106 to present the whiteboard image on thedisplay screen 82 to provide quick visual feedback to the user. A copyof the whiteboard image may also be sent to a designated secondarystorage location such as a personal computer forming part of thedistributed computer network 40. The image can also be posted to anInternet accessible site as disclosed in U.S. Patent ApplicationPublication No. US2004/0201698 to Keenan et al.

Once the high-resolution whiteboard image is available, if desired, auser can select a print command using the option buttons on the housing80. When the CPU 100 receives a print command, the CPU 100 outputs thehigh-resolution whiteboard image to the printer driver 104 which in turnoutputs the whiteboard image either to a printer coupled to the printerdriver port or to the network interface controller 108 so that theelectronic image can be printed by a network printer in the distributedcomputer network 40.

When the user is finished a session, the user simply needs to push theclose session button 86. If the user wishes to continue using the system20, a new session must be opened by pushing the open session button 84.Images captured during the new session are saved and posted separately.

Although the system 20 is described as including a controller thatreceives the image data from the digital cameras 70 a and 70 c, theimage data can be routed directly to a personal computer for processingand storage.

In addition, rather than requiring the capture image button 88 to bedepressed in order to capture images of the whiteboard 22, the CPU 100can be programmed to condition the digital cameras 70 a and 70 c toacquire low resolution images of the whiteboard 22 at specifiedintervals. Each set of captured low resolution images is cropped,cleaned, stitched and analyzed for obstacle presence in the mannerdescribed above. Once a whiteboard image has been captured devoid of anobstacle, the digital cameras 70 a and 70 c are conditioned by the CPU100 to capture high-resolution images.

Furthermore, if desired, each low resolution image can be compared withthe previous captured low resolution whiteboard image to determine ifany changes in the information recorded on the whiteboard 22 haveoccurred. If no changes in recorded information have occurred, thecaptured low resolution whiteboard image are not processed. In thismanner, even though the digital cameras 70 a and 70 c are conditioned toacquire images at selected intervals, the captured images are onlyprocessed to detect the presence of an obstacle if they include newinformation.

Alternatively, the CPU 100 can be programmed to monitor the lowresolution images captured by the digital cameras 70 a and 70 ccontinuously to determine when an obstacle moves into and out of thefields of view of the digital cameras 70 a and 70 c. As soon as anobstacle has moved out of the fields of view of the digital cameras, theCPU 100 conditions the digital cameras 70 a and 70 c to capturehigh-resolution images immediately. In this manner, a change in obstaclepresence is used as a cue to capture high-resolution images of thewhiteboard 22.

If desired, greyscale processing can be applied to the difference imageto turn the difference image into a black on a white image. Duringgreyscale processing, a threshold is applied to the negative differenceimage to convert the negative difference image into a binary (black andwhite) image. The threshold value can have a value ranging from 0 to255. The threshold value that is selected depends on the degree ofobstacle detect sensitivity that is desired. A threshold value equal to128 has been found to yield good results in a variety of conditions.

After thresholding, the region of the binary image close to the framesurrounding the whiteboard is excluded and the remaining portion of thebinary image is examined to detect clusters of black pixels. In thisinstance, if the thresholded difference image includes clusters of blackpixels above a threshold value, an obstacle is considered to be presentin the captured low resolution whiteboard image.

Depending on the quality of the low-resolution images captured by thedigital cameras 70 a and 70 c, obstacle detection may be limited to theof frame portion of the whiteboard area. Typically, obstacles movinginto and out of captured images will extend through the whiteboard frame22 b.

Turning now to FIG. 8, an alternative whiteboard for use with thecamera-based system is shown. In this embodiment, like referencenumerals will be used to indicate like components with a “200” added forclarity. Similar to the previous embodiment, the whiteboard 222 includesa generally planar rectangular board surface 222 a bordered by a frame222 b. An elongate tool tray 224 is disposed slightly below the boardsurface 222 a and supports tools in the form of dry-erase ink pens andan eraser.

An optical switch 300 is positioned on the board surface 222 a adjacentits lower left-hand corner. The optical switch 300 includes arectangular frame 302 and a slider 304 moveable horizontally along theframe 302 between left and right positions. Pictograms 306 are providedon the board surface 222 a in the area encompassed by the frame 302 todirect a user to move the slider 304 from one side of the frame 302 tothe other in order to condition the system 20 to capture images of thewhiteboard 222. Those of skill in the art will appreciate that theoptical switch may be located at basically any location within thefields of view of the cameras 70 a and 70 c.

In this embodiment, the CPU 100 conditions the digital camera 70 cacquire a low resolution image of the whiteboard at specified intervals.When the digital camera 70 c acquires a low resolution image, theacquired low resolution image is compared with a previously captured lowresolution image to determine if the position of the slider 304 haschanged. If the position of the slider is the same, the processcontinues. If the position of the slider has changed, the CPU 100conditions both digital cameras 70 a and 70 c to acquire low resolutionimages of the whiteboard 222. The acquired low resolution images arethen cropped, cleaned, stitched and analyzed for obstacle presence inthe manner described above.

As will be appreciated, in this embodiment the optical switch 300 whenrecognized as changing positions provides a trigger or cue to captureimages of the board surface 222 a. Alternative optical switchconfigurations can of course be used provided a change in condition ofthe optical switch can be determined from the captured images. Forexample, the optical switch 300 may include a mechanical button thatwhen depressed moves the slider 304 from one side of the frame 302 tothe other. The slider 304 can of course be replaced with another type ofelement that moves between positions to trigger or cue image capture.Further, actuation of the optical switch 300 may be used as a cue toinhibit image capture.

In the above-described embodiments, the digital cameras 70 a and 70 care described as capturing low resolution images that are processed todetect the presence of an obstacle prior to capturing high-resolutionimages. If desired, high-resolution images can be captured by thedigital cameras 70 a and 70 b and processed by the CPU 100 to detect thepresence of an obstacle. In this case, when high-resolution images arecaptured and no obstacle is present, the high-resolution images arefurther processed as previously described thereby avoiding the need torecapture images of the whiteboard.

Obstacle detection in the above-described embodiments is used as atrigger or cue to inhibit processing of whiteboard images. If desired,obstacle detection can of course be used as a trigger or cue to captureand process whiteboard images, which may be advantageous in certainenvironments.

Although preferred embodiments of the present invention have beendescribed, those of skill in the art will appreciate that variations andmodifications may be made without departing from the spirit and scopethereof as defined by the appended claims.

1. A system for capturing an image of a target area on which information is recorded comprising: at least one imaging device capturing an image of said target area; and a processor in communication with said at least one imaging device, said processor receiving image data from said at least one imaging device and processing said image data to detect the presence of obstacles in the captured image, wherein during said processing said processor: compares the captured image with a reference image and computes a negative difference image by calculating, for corresponding pixels in said reference and captured images the pixel value: (255−|R _(ij) −C _(ij)|) where: R_(ij) is the binary form of the pixel at the i^(th) row and j^(th) column in the reference image; and C_(ij) is the binary form of the pixel at the i^(th) row and j^(th) column in the captured image; and counts the number of pixels of the difference image having values suggestive of an obstacle and compares the number with a threshold value to detect the presence of an obstacle.
 2. A system according to claim 1 wherein said processor further processes said captured image if no obstacle is detected therein.
 3. A system according to claim 2 wherein said processor conditions said at least one imaging device to capture another image of said target area if an obstacle is detected.
 4. A system according to claim 3 wherein said target area is a whiteboard on which information is recorded using a writing implement.
 5. A system according to claim 2 wherein during said further processing said processor displays said captured image.
 6. A system according to claim 2 wherein during said further processing said processor posts said captured image to an Internet accessible site.
 7. A camera-based system for capturing an image of a target area comprising: a generally horizontally extending boom assembly, said boom assembly being positioned above a target area on which information is recorded; at least one digital camera mounted on said boom assembly at a location spaced from the plane of said target area, said at least one digital camera being oriented so that the field of view thereof encompasses said target area; and a processor in communication with said at least one digital camera, said processor receiving image data from said at least one digital camera and processing said image data to detect the presence of an obstacle in the captured image, said processor conditioning said at least one digital camera to acquire another image of said target area if the presence of an obstacle in said captured image is detected, wherein during said processing, said processor: compares the captured image with a reference image and computes a negative difference image by calculating, for corresponding pixels in said reference and captured images the pixel value: (255−|R _(ij) −C _(ij)|) where: R_(ij) is the binary form of the pixel at the i^(th) row and j^(th) column in the reference image; and C_(ij) is the binary form of the pixel at the i^(th) row and j^(th) column in the captured image; and counts the number of pixels of the difference image having values suggestive of an obstacle and compares the number with a threshold value to detect the presence of an obstacle in the captured image.
 8. A camera-based system according to claim 7 wherein said boom assembly supports a plurality of digital cameras, each of said digital cameras having a field of view that encompasses a different section of said target area, fields of view of adjacent digital cameras overlapping slightly, said processor stitching image data from said plurality of digital cameras to form said captured image.
 9. A camera-based system according to claim 8 wherein said boom assembly supports a pair of digital cameras.
 10. A camera-based system according to claim 7 wherein said boom assembly includes a wall mount, a boom extending outwardly from said wall mount and a camera head on a distal end of said boom, said camera head supporting said at least one digital camera.
 11. A camera-based system according to claim 10 wherein said wall mount is releasably coupled to a wall plate secured to a wall surface.
 12. A camera-based system according to claim 7 wherein said processor receives low resolution image data from said at least one digital camera and processes said low resolution image data to detect the presence of an obstacle in the captured image, said processor conditioning said at least one digital camera to acquire a high-resolution image of the target area in the absence of an obstacle in the captured image.
 13. A camera-based system according to claim 12 wherein said processor processes said high-resolution image to highlight writing on said target area.
 14. A camera-based system according to claim 12 wherein said processor has Internet server capabilities and is coupled to a distributed computer network to allow said captured high-resolution image to be accessed by a user through an Internet browser.
 15. A camera-based system according to claim 14 wherein said processor is a dedicated appliance.
 16. A camera-based system according to claim 14 wherein said processor is a personal computer.
 17. A camera-based system according to claim 7 wherein said processor receives high-resolution image data from said at least one digital camera and processes said high-resolution image data to detect the presence of an obstacle in the captured image, said processor further processing said high resolution image to highlight writing on said target area in the absence of an obstacle in the captured image.
 18. A camera-based system according to claim 17 wherein said processor has Internet server capabilities and is coupled to a distributed computer network to allow said captured high-resolution image to be accessed by a user through an Internet browser.
 19. A camera-based system according to claim 18 wherein said processor is a dedicated appliance.
 20. A camera-based system according to claim 18 wherein said processor is a personal computer.
 21. A method of detecting the presence of an obstacle in front of a background surface on which information is to be recorded, in an image of said background surface captured by at least one imaging device, said method comprising the steps of: receiving by a processor image data from the at least one imaging device; comparing the image data with a reference image and computing a negative difference image by calculating, for corresponding pixels in said reference image and image data the pixel value: (255−|R _(ij) −C _(ij)|) where: R_(ij) is the binary form of the pixel at the i^(th) row and j^(th) column in the reference image; and C_(ij) is the binary form of the pixel at the i^(th) row and j^(th) column in the image data; and examining the negative difference image to determine if the negative difference image has pixels with values suggestive of an obstacle; and conditioning said at least one digital camera to acquire another image if the presence of an obstacle in said captured image is detected.
 22. The method of claim 21 wherein during said examining, the number of pixels having values suggestive of an obstacle is counted and compared with a threshold value.
 23. A system for capturing an image of a target area on which information is recorded comprising: at least one imaging device capturing an image of said target area; and a processor in communication with said at least one imaging device, said processor receiving image data from said at least one imaging device and processing said image data to detect the existence of an obstacle in the captured image, wherein during said processing said processor compares the captured image with a reference image to compute a negative difference image and examines the negative difference image to determine if pixels values thereof are suggestive of the existence of an obstacle, and wherein said negative difference image is computed by calculating, for corresponding pixels in said reference and captured images the pixel value: (255−|R _(ij) −C _(ij)|) where: R_(ij) is the binary form of the pixel at the i^(th) row and j^(th) column in the reference image; and C_(ij) is the binary form of the pixel at the i^(th) row and j^(th) column in the captured image.
 24. A system according to claim 23 wherein said processor further processes said captured image if no obstacle is detected therein.
 25. A system according to claim 24 wherein said processor conditions said at least one imaging device to capture another image of said target area if an obstacle is detected.
 26. A system according to claim 25 wherein said target area is a whiteboard on which information is recorded using a writing implement.
 27. A system according to claim 24 wherein during said further processing said processor displays said captured image.
 28. A system according to claim 24 wherein during said further processing said processor posts said captured image to an Internet accessible site.
 29. A camera-based system for capturing an image of a target area comprising: a generally horizontally extending boom assembly, said boom assembly being positioned above a target area on which information is recorded; at least one digital camera mounted on said boom assembly at a location spaced from the plane of said target area, said at least one digital camera being oriented so that the field of view thereof encompasses said target area; and a processor in communication with said at least one digital camera, said processor receiving image data from said at least one digital camera and processing said image data to detect the existence of an obstacle in the captured image, said processor conditioning said at least one digital camera to acquire another image of said target area if the existence of an obstacle in said captured image is detected, wherein during said processing, said processor compares the captured image with a reference image to compute a negative difference image and examines the negative difference image to determine if pixel values thereof are suggestive of the existence of an obstacle, and wherein said negative difference image is computed by calculating, for corresponding pixels in said reference and captured images the pixel value: (255−|R _(ij) −C _(ij)|) where: R_(ij) is the binary form of the pixel at the i^(th) row and j^(th) column in the reference image; and C_(ij) is the binary form of the pixel at the i^(th) row and j^(th) column in the captured image.
 30. A camera-based system according to claim 29 wherein said boom assembly supports a plurality of digital cameras, each of said digital cameras having a field of view that encompasses a different section of said target area, fields of view of adjacent digital cameras overlapping slightly, said processor stitching image data from said plurality of digital cameras to form said captured image.
 31. A camera-based system according to claim 30 wherein said boom assembly supports a pair of digital cameras.
 32. A camera-based system according to claim 29 wherein said boom assembly includes a wall mount, a boom extending outwardly from said wall mount and a camera head on a distal end of said boom, said camera head supporting said at least one digital camera.
 33. A camera-based system according to claim 32 wherein said wall mount is releasably coupled to a wall plate secured to a wall surface.
 34. A camera-based system according to claim 29 wherein said processor receives low resolution image data from said at least one digital camera and processes said low resolution image data to detect the existence of an obstacle in the captured image, said processor conditioning said at least one digital camera to acquire a high-resolution image of the target area in the absence of an obstacle in the captured image.
 35. A camera-based system according to claim 34 wherein said processor processes said high-resolution image to highlight writing on said target area.
 36. A camera-based system according to claim 34 wherein said processor has Internet server capabilities and is coupled to a distributed computer network to allow said captured high-resolution image to be accessed by a user through an Internet browser.
 37. A camera-based system according to claim 36 wherein said processor is a dedicated appliance.
 38. A camera-based system according to claim 36 wherein said processor is a personal computer.
 39. A camera-based system according to claim 29 wherein said processor receives high-resolution image data from said at least one digital camera and processes said high-resolution image data to detect the existence of an obstacle in the captured image, said processor further processing said high resolution image to highlight writing on said target area in the absence of an obstacle in the captured image.
 40. A camera-based system according to claim 39 wherein said processor has Internet server capabilities and is coupled to a distributed computer network to allow said captured high-resolution image to be accessed by a user through an Internet browser.
 41. A camera-based system according to claim 40 wherein said processor is a dedicated appliance.
 42. A camera-based system according to claim 40 wherein said processor is a personal computer.
 43. A method of detecting the presence of an obstacle in front of a background surface on which information is to be recorded, in an image of said background surface captured by at least one imaging device, said method comprising the steps of: receiving by a processor image data from the at least one imaging device; comparing the image data with a reference image and computing a negative difference image by calculating, for corresponding pixels in said reference image and image data the pixel value: (255−|R _(ij) −C _(ij)|) where: R_(ij) is the binary form of the pixel at the i^(th) row and j^(th) column in the reference image; and C_(ij) is the binary form of the pixel at the i^(th) row and j^(th) column in the image data; and examining the negative difference image to determine if the negative difference image has pixels with values suggestive of an obstacle; and conditioning said at least one imaging device to acquire another image if the presence of an obstacle in said captured image is detected.
 44. The method of claim 43 wherein during said examining, the number of pixels having values suggestive of an obstacle is counted and compared with a threshold value. 